This invention is directed toward a gate for a prefeeder which is designed to take a stack of substantially flat articles and provide them in a desired shingled arrangement for further processing.
It is oftentimes difficult to maintain the proper shingled relationship throughout a continuous operation of the prefeeder. Variations in the height of the stacked signatures provided to the prefeeder, which necessarily translates into variations in the weight of the stack and the magnitude of the compressive force acting upon each article in the stack, adversely affects the quality of the resulting shingle. Such problems are intensified with respect to smaller size blanks or signatures.
Examples of prior art prefeeder gates can be found in U.S. Pat. No. 4,062,532 to Peter, et al. and U.S. Pat. No. 4,771,896 to Newsome, these two references being incorporated herein by reference. Such prior art devices employ a control gate having an adjustable-height throat which regulates the number of blanks passing through the gate and thereby controlling the degree of shingling of the blanks. By controlling the degree of shingling, faster and more efficient processing of the resulting shingled articles is possible. The effectiveness of such prior art structures in inducing proper shingling, however, diminishes as the size of the conveyed articles decreases.
Floating gates in general are known in the art for the purpose of admitting only one sheet or article in a stack at a time, as opposed to a plurality of articles in a shingled arrangement. For instance, U.S. Pat. No. 4,961,566 to Labombarde (deceased) discloses a sheet feeder including a spring-biased gate, the lower end of which is disposed above the conveying surface by a predetermined distance. In operation, a sheet lifter causes the gate to rise along with the stack of sheets lifted. A single sheet is admitted through the gate only after the sheet lifter, and thus the stack of sheets, have been completely lowered. For further example, U.S. Pat. No. 3,941,373 to Stange discloses a floating sheet separator biased upwardly by a spring into contact with an upper belt. The force of the spring prevents admission of more than one sheet at a time. While such devices may be suitable for their respective intended purposes, they are not suited to admit multiple articles at one time, e.g., articles conveyed in a shingled arrangement. Accordingly, there is room for improvement within the art.